Sodium Channel Toxicity

Classily, sodium channel toxicity was described in tricyclic overdoses,96 but many drugs can cause toxic sodium channel effects including antiarrhythmics (e.g., lidocaine, phenytoin, propafenone, flecainide, amiodarone, sotalol), antiepileptic medications (e.g., carbamazepine, lamotrigine), selective serotonin reuptake inhibitors (e.g., citalopram, fluoxetine), antihistamines (e.g., diphenhydramine), propranolol, cyclobenzaprine, and others. ECG features include a widened QRS, prolonged QT, right axis deviation, tall terminal R in aVR. Patients with sodium channel toxicity need a sodium load. One of the most effective ways of delivering sodium is via 8.4% sodium bicarbonate, which has the dual effect of loading with extracellular sodium and alkalinizing the serum pH, favoring the neutral (i.e., non-ionized) form of the drug and making it less available to bind to sodium channels. Give 1-2 ampules of 8.4% sodium bicarbonate and repeat the ECG, continue until the QRS is < 100 ms to reduce the risk of seizures and arrythmias.